Drill rig and methods for directional drilling

ABSTRACT

A device for measuring inclination is suspended to a cable passing through a duct formed in the rods of the drill string. A mechanism for winding and unwinding the cable allows to raise and drop the measuring device within the lowermost rod, engaging it with or disengaging from a mule shoe. This is performed without the need to unscrew the rods and open the string. A valve element may close the duct through which the cable passes. In one embodiment, directional drilling is performed supplying low pressure fluid through tubular rods having a single duct. In another embodiment, high pressure fluids are supplied through rods having two or more coaxial ducts.

TECHNICAL FIELD

The present invention pertains to the field of civil engineering andrelates to a drill rig and methods for performing directional drillingin the ground. The drilling operations are aimed, particularly but notexclusively, at executing jet grouting consolidations.

BACKGROUND ART

With soil perforations known as “directional drillings”, deviations arechecked at certain phases of the drilling. Corrections are consequentlymade either to keep the axis of the drilling within certain limits ofdeviation from the desired theoretical axis, or to keep a giventrajectory of the drilling according to design requirements.

In order to detect the inclination during a drilling step, a knownmethod provides for mounting a device for detecting inclination fixedlysecured to the bottom of the drill string. A number of electricalconnections have to be made as new drill pipes are added, to extend aconductor line from the device up to a power supply on ground surface.Unless special shock absorbers are used, this method does not preservethe device from shocks and vibrations transmitted from the drill.

Another known system (FIG. 1) provides that a tool 40 for measuringinclination is periodically introduced and lowered through the hollowrods of a drill string 14. Inclination is typically measured every 3-6meters as the drilling proceeds. According to established practice inoilfield applications, the device for measuring inclination may be ofthe gyroscopic type, or of the electromagnetic accelerometer, usuallyincluding a compass associated with an inclinometer. A known method ofthis type uses a winch to lower the inclination measuring device 40within the rods. The measuring device is suspended by a steel cable 22containing an insulated electrical conductor. Whenever the inclinationis to be measured, the drilling must be stopped, the drill string mustbe opened by unscrewing the rods, and the measuring device must beintroduced through the inner cavity of the rods. A device known in thefield as a “mule shoe” allows to orient the measuring device accordingto a known direction, which coincides with the direction of thelowermost element of the drill string (usually built in non-magneticsteel) and the drilling bit integral with it.

In other instances, where real-time inclination data are not required,the device may be lowered by means of a standard cable without anelectrical conductor, and the inclination data may be downloaded from abuffer of the device after it has been brought back up to the surface.However, the above method is unsuitable if inclination data are neededin real time, for example, to promptly correct the direction of thedrilling.

A typical conventional method, regardless of the type of instrumentationused, involves a sequence of operating steps comprising:

a) interrupting the supply of the drilling fluid and stopping thedrilling;b) opening of the drill string, by unscrewing the rods;c) lowering the measuring device until the “mule shoe” is engaged;d) measuring the inclination by orienting the string through a clamp,since the rotary in this step is not connected to the string;measurement of the inclination may be performed at 4 different angularpositions spaced 90° from each other;e) retrieving the measuring device back up to surface;f) closing the drill string by re-screwing the rods.

For the cases requiring the inclination to be corrected, step f) must befollowed by a subsequent step in which a deviated bore section isdrilled, thereby correcting the inclination of the borehole. Then,before resuming drilling, it is necessary to repeat the sequence ofsteps a) to f).

U.S. Pat. No. 3,718,194 (to Hering et al.) discloses an apparatus fororienting a borehole device in a borehole within the context of drillingoil wells. An orienting tool is positioned in a drill pipe and providedwith a conductor cable to the surface. An instrument in the toolprovides a measurement for indicating the orientation (the so-called“high side”) of the tool in the wellbore. Instrument measurements aretransmitted by the conductor cable to the surface for surface read-out.A surface indicator provides the readout in a manner which is indicativeof degrees of rotation of a reference on the tool to the right or leftof the high side of the hole. The tool may then be rotated andsubsequent readings taken to determine the position of the tool untilthe bit is oriented, whereupon drilling proceeds. Such readings can betaken continuously throughout the drilling operation.

U.S. Pat. No. 2,207,505 (to Bremner et al.) discloses a mule shoe toolfor orienting a drill pipe in the bore of an oil well.

SUMMARY OF THE INVENTION

The present invention aims at speeding up a directional drilling,eliminating some of the steps mentioned herein above. Another object ofthe invention is to keep the inclination measuring device within thestring during the drilling while preserving the device from vibrationsand shocks transmitted from the drill string.

The above and other objects and advantages, which will be betterunderstood from the ensuing description, are achieved according to theinvention by methods defined in the appended claims. According toanother aspect, the invention provides drill rigs for implementing thesemethods.

In brief, a device for measuring inclination is suspended to a cablepassing through a duct formed by the cavity of the rods of the drillstring. A mechanism for winding and unwinding the cable allows to raiseand drop the measuring device within the lowermost rod, engaging it withor disengaging from the mule shoe. This is performed without the need tounscrew the rods and open the string. A valve element may close the ductthrough which the cable passes. Two embodiments are provided. Oneembodiment is particularly suitable for the execution of directionaldrilling with the supply of low pressure fluid with tubular rods havinga single duct. A second embodiment is specific for directional drillingwith the supply of high pressure fluids and rods having two or morecoaxial ducts.

BRIEF DESCRIPTION OF THE DRAWINGS

A few preferred but not limiting embodiments of the methods and drillrig according to the invention will now be described; reference is madeto the accompanying drawings, in which:

FIG. 1 is a schematic view of a step of measuring the inclination of adrilling according to the prior art;

FIG. 2 is a schematic elevation view of a drill rig for executingperforations intended for jet grouting consolidations with detection ofthe borehole inclination, according to an embodiment of the invention;

FIGS. 3A, 3B and 3C are schematic views in vertical cross section, to anenlarged scale, of part of the drill rig of FIG. 2, in three differentoperational positions;

FIGS. 4A and 4B are elevation views, as viewed from to two differentangles, of a device for measuring inclination with a “mule shoe” guidefor its angular orientation;

FIG. 5 is a partial view of the vertical section, further enlargedscale, of the lower part of the string of rods shown in FIGS. 3A-3C;

FIG. 6 is a schematic cross-sectional view to enlarged view of a headthe supply of fluid in the apparatus of FIGS. 3A-3C;

FIG. 7 is an enlarged view of a detail of FIG. 3A; and

FIGS. 8 and 9 are schematic elevational views, in two differentoperational conditions, of an apparatus according to a furtherembodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 2, a self-propelled vehicle 10 carries a drilling mast11, in this example illustrated in an upright or vertical position.Slidably mounted along the mast 11 is a top-drive rotary head 12. Therotary head serves to impart rotation and sliding movement (push-pull)to a string 14 of hollow rods for carrying out soil perforation ordrilling. The rotary head may be driven by an associated hydraulic motorgear 12 b. A boring tool 16 is fixed at the bottom end of the string 14of rods.

The general structure of a drilling mast and of the actuating means of arotary head are to be considered generally known. Consequently, thepresent description will describe in detail only those elements ofspecific importance and interest for the purposes of implementing of theinvention. For the construction of the parts and elements not shown indetail, such as the motor assembly for driving the rotary head and thedrive systems of the boring tool, reference may be made to any apparatusof known design. In the description and in the drawings, two differentembodiments of the method are illustrated, which differ mainly in thelevel of pressure of the fluid supplied to the string.

FIGS. 2, 3A-C, 5-7 show an arrangement which is suitable for operationwith a boring tool 16 operating with a drilling fluid at low pressure,for example air-powered hammers or non-percussive bits able to work withwater pressures not exceeding 50 bars, approximately. FIGS. 8 and 9depict an apparatus suitable for working with a boring tool operativelyassociated with a high pressure fluid, for example an in-the-hole hammerpowered by high pressure water or rotation bits such as tricone rockbits, three (or four) blade drag bits and the like. As an alternative,asymmetric non-rotating thrust directional bits may be used, ordirectional active tools, such as “mud motors”. The type of boring toolmay vary depending on the applications.

For an operational mode with the use of air or low pressure drillingfluid, the string 14 may comprise a set of tubular hollow rods 14 a-14 cwhich define a central longitudinal axis x and each have an axiallyextending inner cavity 15, preferably a cylindrical cavity coaxial tothe longitudinal axis x. As understood here, terms and expressionsindicating positions and orientations, such as “longitudinal”, “axial”or “radial” should be interpreted with reference to the longitudinalaxis x. In the prevailing mode of use, the x axis is vertical; however,the method is applicable also for perforations inclined with respect toa vertical direction.

When the rods are joined, in a manner known per se, the inner cavities15 of the rods are axially aligned and interconnected so as to formtogether a duct through which a drilling fluid can be conveyed, such aswater or air or a grout consolidating mixture, according torequirements. The example of FIGS. 3A-3C shows three rods 14 a, 14 b, 14c. It is understood that the total number of rods used may be greaterthan three, depending on the depth of the work of consolidation to becarried out.

The lowermost or bottom hollow rod 14 c has one or more bottom nozzles18 a, in this example, two in number, communicating with the internalcavity 15, for discharge of drilling fluid. The boring tool 16 isintegral with the lower end of the lowermost hollow rod 14 c.

In the illustrated example, just above the bottom nozzle 18 a there areprovided radially oriented side nozzles 18 b, which open on an outerside surface of the bottom rod. Schematically designated 18 c is a valveelement which, under fluid pressures in excess of a predetermined value,moves so as to occlude the bottom nozzle 18 a and simultaneously openthe side nozzles 18 b to perform a jet grouting injection. In otherembodiments, the side nozzles 18 b can be made in a cylindrical elementcalled a “monitor” which is mounted immediately above of the boringtool. It should be understood that this specific use is not intended tolimiting and that the method may also be implemented with different jetgrouting technologies.

In a manner known per se, the inner cavity 15 of the bottom 14 c of therod provides an internal projection 17 (FIG. 5), radially protrudingtowards the inside of the cavity and defining a predetermined angularposition with respect to the central longitudinal axis x of the string14.

The rotary head 12 has an axially extending through cavity 13 and islockable to the uppermost or top hollow rod 14 a. An upper end 141 a ofthe rod 14 a projects above the top of the through cavity 13 of therotary head and supports a swivel connector 19.

The swivel connector 19 (FIG. 7) comprises two coaxial tubular elements19 a, 19 b, rotatable relative to one another by means of a rollingbearing 19 c. The outer tubular member 19 a of the swivel connector isidly mounted for rotation about the uppermost rod 14 a and can be keptrotationally stationary with respect to the x axis. This may beachieved, for example, by means of a bracket or arm or otheranti-rotation means 21 which engages an outer, rotationally fixedportion 12 a of the rotary head 12 and the swivel connector 19.Designated at 12 c is rotatable portion of the rotary head 12. The innertubular member 19 b of the swivel connector 19 has an axially extendinginner through cavity 20. This cavity is axially aligned andcommunicating with the inner cavity of the rod 14 a and therefore withthe duct 15 formed by the communicating cavities of the joined rods ofthe string.

A cable 22, to which a device (or instrument) 40 for measuringinclination is suspended, passes through the duct formed by the throughcavities of the rods 15 and the cavity 20 passing through the swivelconnector 19.

The internal cavity 20 passing through the swivel connector 19 may beoccluded by an annular valve 30, preferably a pneumatically operatedpinch valve mounted on the outer, stationary element 19 a of the swivelconnector 19. The annular valve 30 is mounted idly mounted for rotationabout the axis x above an upper end of a top rod 14 a of the string andabove the top-drive rotary head.

The annular valve 30 may comprise a flexible body, preferably made ofrubber, which can be closed by radially tightening or clamping it aroundthe cable 22. The annular valve 30 may be controlled in opening andclosing in different ways (for example electrically, pneumatically,hydraulically, or manually), so as to open or seal the passage of thecable 22 and the duct formed by the rods and the swivel connector 19.

The device or instrument 40 for measuring inclination is mounted on aguiding element 29, per se known in the drilling field as “mule shoe”.The guiding element provides a guide 28 for example in the form of aflared groove, downwardly widening and upwardly tapering. As the device40 is lowered into the drill string, the lower and wider part of theguiding groove 28 meets the inner projection 17 in the cavity of thelowermost rod and guides the device 40 downwards, at the same timeorienting it in a predetermined angular position with respect to thex-axis, the device reaches a stable position in which the innerprojection 17 abuts against the upper end 27 of the guiding groove 28.

According to an embodiment (not shown), the guiding element 29 may beprovided with a switch or other switching device (such as a sensor) thatcloses an electrical circuit (not shown) when the measuring device 40reaches the correct angular position with respect to the lowermost rod.This way an operator may be sure that the inclination has been detectedcorrectly.

The device 40 may include a tracking or guiding sensor or probe formeasuring inclination, for example a Paratrack® or TrueTrack device. Themeasuring device 40 may incorporate an inclinometer and a compass, suchas a triaxial magnetometer, already used in the field of directionaldrilling. The selection of the particular device for measuringinclination is not to be considered limiting as regards theimplementation of the present method.

The inner cavities 15 of the rods of the string have an internaldiameter sufficient to ensure easy handling of the measuring device 40within the string. For example, the inner cavities 15 may have aninternal diameter between 30 and 100 mm wide.

The cable 22 may be a steel cable. Optionally, the cable 22 may containin its interior an insulated electrical cable (e.g. of a Camesa cable orthe like). Alternatively, the cable 22 may be an electric cablereinforced on its outside.

Schematically designated 23 in FIG. 6 is a fluid supplying head (or topswivel, or rotary air/water swivel), in this example mounted on anintermediate rod element 14 b of the string. The head 23, known per se,supplies a drilling fluid (air, water, polymer additives, bentonite,grout mixtures) that is introduced in the central cavity 15 through oneor more lateral inlet openings 24 formed in the rod element 14 b. Thesupplying head 23 is idly mounted for rotation on rod element 14 bthrough one or more rolling bearings 23 a.

A tubular body 26, containing a swivel valve member 30 a able towithstand high pressures (e.g. in the order of 300-500 bars), may bemounted in the drill string above the fluid supplying head 23 in orderto selectively occlude the central duct 15.

The drill rig comprises a winch 31 (FIG. 2) or another winding andunwinding mechanism for moving the cable 22 and the measuring device 40.In the illustrated example, the winch 31 is positioned immediatelybehind the mast 11.

FIG. 3A shows an arrangement for measuring inclination of the drilledborehole. The measuring device 40 is located in the lowest positionreached within the bottom rod 14 a. In this position, the device 40 isoriented in an angular position determined by engagement of the guidingelement 29 with the internal projection 17.

During a drilling step (FIG. 3B), the measuring device 40 can be heldwithin the string of rods, either in a condition where the mule shoe isengaged, or suspended from the cable 22 in a raised position above theinternal projection 17. When suspended, the measuring device 40 is notintegral with the bottom rod 14 c, and therefore is not negativelyaffected by vibrations and shocks transmitted by the boring tool 16 tothe bottom rod of the string. It is convenient to perform drilling withthe measuring device 40 engaged in the mule shoe because this modeallows to obtain inclination data in real time. It will be understoodthat this operating mode is only applicable when the boring tool is nota percussive tool.

The annular valve 30 is kept closed around the cable 22 during the stepsof drilling and/or injecting fluid through the drill string, to preventthe escape of fluid from the top of the string, particularly from thetop of the duct formed by the communicating cavities of the rods. Whenthe drill string is rotated integrally with the rotary head, the valve30 is kept rotationally stationary due to the swivel connection 19,which is idly mounted for rotation on the rotary head 12. The measuringdevice 40, suspended from the cable 22, is rotationally stationary withrespect to the rotating string. As a result of the tightening of theannular valve 30 on the cable 22, the measuring device 40 is verticallyor axially constrained to the annular valve 30, and follows themovements of axial translation of the rotary head 12 along the mast 11.

When the inclination of the drilled borehole is to be measured, asequence of operating steps may be as follows.

-   -   The supply of drilling fluid is interrupted and the drilling is        stopped.    -   Without needing to unscrew the rods to open the string, the        inclination measuring device 40 may be let down to lowest        position it may reach inside the bottom rod 14 c until the        device 40 engages the internal protrusion 17. Advantageously,        the device 40 is already present in suspended condition within        the string. By engaging the internal projection 17, the guiding        element 29 (FIG. 3A) orientates the measuring tool 40 in a given        angular position.    -   The inclination of bottom rod 14 c is measured by the device 40.        The inclination may be advantageously measured without releasing        the rods from the rotary head. The methods of measuring the        inclination are not limiting. For example, measurements may be        taken in 4 different angular positions spaced 90° from one        another, in accordance with the methods disclosed in patent        publication US 2013/020129 A1, incorporated herein by reference        in its entirety.    -   After measuring the inclination, the device 40 may be raised        again so as to disengage it from the internal projection 17        release it rotationally from the string 14. The measuring device        may be fully recovered, i.e. pulled out of the string without        opening it. Alternatively, the device 40 may be kept suspended        within the string (FIG. 3B).

The drilling operations may then be resumed or steps may be followed tocorrect the inclination of the borehole. To correct the inclination, themeasuring device 40 is preferably suspended within the string to protectit from the vibrations generated by the downhole boring tool. Maneuversfor correcting inclination are known in the art, and therefore will notbe described herein. Suffice it to mention that inclination correctionusually provides a further sinking or penetration of the boring tool fora short length, of the order of some tens of inches, without setting thestring in rotation, so as to deviate appropriately the direction of thedrilling, depending on the measured values of inclination. In this step,the device 40 may remain engaged in the mule shoe.

The annular valve 30 may be closed to seal the top of the string whenthe measuring device has been pulled out of the string. During rotationof the string, if the measuring device 40 has not been completelyremoved, the annular valve 30 is locked in the closed position aroundthe cable 22, ensuring hydraulic seal.

It will be appreciated that the present method allows to measure theinclination of the drilling without the need to unscrew the rods inorder to open the string and introduce the inclination measuring devicein the string, and without having to re-screw the rods once theinclination has been measured and the measuring device has beenwithdrawn from the string.

It will also be appreciated that, due to the above describedarrangement, it is possible to supply pressurized fluid in order toperform the drilling without the need to remove the measuring devicefrom the string, and, unless a percussive boring tool is used, withoutdisengaging the mule shoe.

The mechanism 31 for winding and unwinding of the cable 22 may beequipped with automatic devices that facilitate the operator's work. Therig may be equipped with a control system that stores the depth reachedby the measuring device 40.

The control system may be set to automatically slow down the winchbefore the measuring device reaches a preset depth where it has beenprogrammed to measure the inclination. Advantageously, the controlsystem can be set to cause the measuring device 40 to raiseautomatically up to a predetermined level just before the drillingrestarts, in order to protect the device from the vibrations induced bythe boring tool.

FIG. 3C shows the arrangement of the apparatus during a jet groutingstep. Once the drilling is completed, and after the measuring device hasbeen extracted out of the string 40, the duct 15 can be occluded orsealed tightly above the fluid supplying head by rotating the rotatablevalve element 30 a in the closed position (FIG. 3C). Then, the stringmay begin to raise and perform a jet grouting injection in the liftmode, using the fluid supplying head 23 to pump pressurized grout (forexample at 300-500 bars) through the central duct 15. The valve element18 c, which is activated automatically due to the pressure, will occludethe bottom holes 18 a and force the fluid to exit from the radiallyoriented side nozzles 18 b.

Referring now to FIGS. 8 and 9, there is illustrated an embodiment of amethod of performing directional drilling with a drill rig working witha high pressure fluid. The drill rig comprises a top-drive rotary head12 similar to that described with reference to FIGS. 2 and 3A-3C,lockable to a drill string 14. The string includes a tubular top rod 14a, in this example with a single passage or through cavity 15, and anumber of dual passage rods 14 b, 14 c (two in number in the illustratedexample).

Fixed to the bottom rod 14 c is a boring tool 161 capable of operatingwith a drilling fluid supplied at high pressure. The boring tool 161 mayfor example be a an in-the-hole hammer powered by high pressure water(known as “Wassara™”) or a rotating bit (a tricone, or a three bladedrag bit) or an asymmetric directional bit (or “slant face bit”) to besupplied with fluid at high pressure.

The top rod 14 a is lockable in the passage 13 of the rotating part 12 cof the rotary head in a manner similar to that described in relation toFIGS. 2 and 3A-3C, except for the fact that for the execution of soilconsolidation with fluids at high pressure, an annular valve of the typeindicated at 30 in FIGS. 3A-3C is not used.

The dual passage rods 14 b, 14 c each comprise two coaxial pipes: aninner pipe 141 b, 141 c, with an internal diameter sufficient to ensurethe passage of a device 40 for measuring inclination, and an outer pipe142 b, 142 c. Each inner pipe has a central cavity 15. The centralcavities 15 of the rods are axially aligned and interconnected so as toform together a first central (or more internal) duct through which afluid can be conveyed, in this example a grout consolidating mixture.

An annular gap forming a second duct 151 is defined between the outerpipes 142 b, 142 c and inner pipes 141 b, 141 c is defined theperipheral (or external), through which drilling fluids can be made topass, typically water or air. These fluids are then injected out of thestring through one or more bottom nozzles 18 a provided in the boringtool 161. The drilling fluids may be introduced into the peripheral duct151 through a supplying head 123 idly mounted for rotation about theouter pipe 142 b, for example by means of one or more rolling bearings(not shown) similarly to the fluid supplying head 23 shown in FIG. 6.The fluid supplying head 123 is arranged below the rotary head 12, inproximity to and in fluid communication with one or more inlet lateralopenings 123 a formed in the outer pipe 142 b.

A consolidating mixture, such as a grout mixture, can be introduced intothe central duct 15 within the inner pipes 141 b, 141 c by a fluidsupplying head 124. The head 124 is idly mounted for rotation about theouter pipe 142 b, similarly to the fluid supplying head 123. The fluidsupplying head 124 is mounted just below the rotary head 12, andprovides fluid communication between an external fluid source (notshown) and the central duct 15 within the inner pipe 151.

In proximity to and in fluid communication with one or more inlet sideopenings 124 a formed in the outer pipe 142 b and with inlet sideopenings 124 c formed in the inner pipe 141 b. The grout is injected outof the string through one or more side nozzles 18 b. The side nozzles 18b can be formed in a monitor mounted immediately above of the boringtool.

The fluid supplying heads 123 and 124 may be conveniently mounted on asame dual passage rod, as in the example illustrated. In otherembodiments (not shown), the two fluid supplying heads may be mounted ontwo distinct rods.

In the embodiment illustrated in FIGS. 8 and 9, the head 124 forsupplying the consolidating mixture is located above or upstream of thehead 123 for supplying drilling fluids.

According to an alternative embodiment (not shown), the two fluidsupplying heads 123 and 124 may be constructed as a single unit.

The swivel connector 19, visible in FIGS. 8 and 9, may be omitted.

A tubular body 26 containing a rotatable valve member 30 a, capable ofwithstanding high pressures (e.g. in the order of 300-500 bars), may bemounted in the drill string above the fluid supplying head 124 toocclude the central duct 15 when this is required.

The device 40 for measuring inclination may be introduced into thestring during any operational step, for example even during thedrilling. The device 40, suspended from a cable 22 in a manner similarto that described with reference to FIGS. 2, 3A-C, may be lowered intothe central duct 15 until it reaches an inward projection 17 protrudingin the central cavity 15 of the bottom rod 14 c to provide angularorientation of the inclination measuring device 40.

FIG. 8 illustrates an operating condition in which the measuring device40 is suspended in the central cavity 15 and detached from the bottomrod, in order to preserve the device 40 from vibrations coming from theboring tool. The central duct 15 has a diameter (for example between 30and 100 mm wide) sufficient to ensure easy handling of the device 40within the string. The rotatable valve member 30 a is rotated into aposition in which it leaves the central duct 15 open and allows thepassage of the cable 22.

During a drilling step, the tool 40 may be left inside the string in thesuspended and raised condition shown in FIG. 8. In this event, the muleshoe allows a quick connection of the measuring device 40 to the bottomrod in order to immediately achieve inclination data just after a stepof correcting the inclination has been completed.

When grout has to be injected as the string moves upwards, after theborehole has been drilled, the measuring device 40 must be completelyremoved from the string, The central duct 15 must be temporarilyoccluded to prevent the fluid from reaching the top of the string (FIG.9). During the injection step, the rotatable valve member 30 a isrotated to close the central duct 15 above the fluid supplying head 124.Then, the consolidating mixture is supplied into the central duct 15through the fluid supplying head 124.

The second, peripheral duct or cavity 151 may be used to injectpressurized air, as typically occurs in a dual-fluid jet process. Thecentral duct 15 may be provided with an automatic valve, shownschematically at 18 c, configured for moving under the action ofpressures in excess of 200-300 bars and putting the central duct 15 influid communication with the side nozzles 18 b, typically made in amonitor.

Preferably, the peripheral duct 151 can communicate with both thenozzles of the bottom of the boring tool and the side nozzles in themonitor.

It will be appreciated that the embodiment shown in FIGS. 8 and 9 allowsto perform, with a same single rig, both the directional drilling andthe following jet grouting operations. The central duct 15 isadvantageously exploited also for guiding and protecting the inclinationmeasuring device 40 (FIG. 8) while high pressure drilling fluids areinjected through the peripheral duct 151.

It will also be appreciated that the cable 22 provides a continuous andperfectly insulated power line which allows power to be supplied anddata collected by the device 40 to be transmitted even when considerabledepths are reached. This allows to dispose of sealed electrical contactsand quick connection electric contacts between the rods, which usuallyincrease the electric resistance and cause electric dispersion, leadingto malfunction of the equipment.

What is claimed is:
 1. A drill rig for directional drilling, comprising:a self-propelled vehicle (10); a drilling mast (11) carried by theself-propelled vehicle; a top-drive rotary head (12), translatable alongan axis (x) parallel to the mast (11), the head having a rotatable part(12 c) rotationally drivable around said axis and defining a throughcavity (13), and a rotationally stationary part (12 a); a string ofthreadedly coupled tubular rods (14) having respective axially extendedcommunicating cavities (15) and defining altogether at least one ductadapted to convey at least one fluid to at least one bore (18) obtainedin a bottom element of the string, wherein the string comprises at leastone upper tubular rod (14 a) lockable in the through cavity (13) of therotatable part (12 c) of the rotary head; at least one fluid supplyingdevice (23, 123, 124) idly mounted for rotation on a rod (14 b) locatedbelow the rotary head, for supplying at least one fluid through the duct(15); a boring tool (16) mounted at the bottom of the string (14) ofrods; a device (40) for measuring inclination suspended by a cable (22)passing through the duct (15) formed by the rods; a winding andunwinding mechanism (31) for moving the cable (22); a mule shoe assembly(17, 28), comprising a guiding surface (28) integral to the device (40)and a key member (17) within a bottom rod (14 c) of the string, adaptedto engage the guiding surface (28) and guide the device in a desiredorientation with respect to the bottom rod (14 c); at least one valvemember (30), associated with the duct (15), and mounted on the stringabove said at least one fluid supplying head and above the top-driverotary head, the valve member being capable of reaching a closureposition closing the duct and an open position opening the duct.
 2. Thedrill rig of claim 1, wherein the valve member (30) is an annular valveidly mounted for rotation about the axis (x) above an upper end of a toprod (14 a) of the string.
 3. The drill rig of claim 2, wherein theannular valve (30) is mounted on the upper end of the top rod (14 a)through the interposition of a swivel connector (19), the swivelconnector having an inner tubular element (19 b) having a throughaxially extending cavity (20) which is communicating and aligned axiallyand rotationally integral with the inner cavity of the upper rod (14 a);an outer tubular element (19 a) which is mounted rotationally idle tothe inner tubular element (19 b) and is integral with the annular valve(30).
 4. The drill rig of claim 3, further comprising an anti-rotationelement (21) which engages a rotationally stationary part (12 a) of therotary head (12) and the outer tubular element (19 b) of the swivelconnector to maintain the outer tubular element (19 b) rotationallystationary.
 5. The drill rig of claim 2, wherein the annular valve (30)is a pneumatically operated pinch valve.
 6. The drill rig of claim 1,wherein the rods of the string have a single central duct (15) andwherein the apparatus comprises a single fluid supplying device (23),mounted below the rotary head, for supplying a fluid through the singleduct (15).
 7. The drill rig of claim 1, wherein: the upper tubular rod(14 a) which is lockable to the rotatable part (12 c) of the rotary headhas a single, axially extending through cavity; the string comprises aplurality of tubular dual-passage rods (14 b, 14 c), wherein eachdual-passage rod comprises two coaxial tubes which have a central,axially extending cavity communicating with the through cavity of theupper tubular rod (14 a) so as to define altogether a first central duct(15) capable of conveying a fluid to at least one bore (18) obtained ina bottom element of the string; an axially extending annular cavitycommunicating with the annular cavities of the other dual-passage rodsso as to define altogether a second peripheral duct (151) adapted toconvey a fluid to at least one bore (18 a) obtained in a bottom elementof the string; two fluid supplying devices idly mounted for rotation onone or two dual-passage rods mounted below the rotary head: a firstfluid supplying device (123) for supplying a fluid through theperipheral duct (151), and a second fluid supplying device (124) forsupplying a fluid through the central duct (15); and wherein the valvemember (30 a) is associated with the central duct (15) and is mountedabove the second fluid supplying device (124).
 8. A method of performingdirectional drilling, comprising the steps of: performing a directionaldrilling in a soil by means of the drill rig of claim 1, supplying adrilling fluid in the duct (15) through the fluid supplying device (23);interrupting the supply of drilling fluid and stopping the motion of therotary head and the string of rods; bringing the at least one valvemember (30, 30 a) into open position; without unscrewing the rods toopen the string, lowering the inclination measuring device (40) into theduct (15), bringing the mule shoe assembly (17, 28) to an engagedcondition so as to orient the inclination measuring device (40) in adesired orientation with respect to the bottom rod (14 c) of the string;measuring the inclination of the bottom rod by means of the device (40);lifting the device (40) by means of the cable (22) so as to disengagethe mule shoe assembly and rotationally release the device (40) from thestring; optionally, performing maneuvers to correct the inclination ofthe string; bringing the at least one valve member (30, 30 a) into theclosed position; resuming drilling and supplying drilling fluid throughthe duct (15).
 9. The method of claim 8, wherein the step of bringingthe valve member (30, 30 a) into the closed position is preceded by thestep of completely removing the measuring device (40) from the string ofrods, pulling the device (40) upward by rewinding the cable (22),without unscrewing the rods of the string.
 10. The method of claim 8,wherein the step of bringing the valve member (30) into the closedposition is performed by hermetically closing the valve member (30)around the cable (22), and the subsequent step of resuming the drillingis performed keeping the measuring device (40) suspended to the cable(22) inside the duct (15), simultaneously keeping the valve memberelement (30) rotationally stationary.
 11. A method of performingdirectional drilling, comprising the steps of: performing a directionaldrilling in a soil by means of the drill rig according to claim 7,supplying a drilling fluid in the second peripheral duct (151) throughthe second fluid supplying device (124); interrupting the supply ofdrilling fluid and stopping the movements of the rotary head and the rodstring; bringing the valve member (30 a) into the open position; withoutunscrewing the rods to open the string, lowering the inclinationmeasuring tool (40) into the first central duct (15), bringing the muleshoe assembly to an engaged condition so as to orient the measuringdevice in a desired orientation with respect to the bottom rod (14 c) ofthe string; measuring the inclination of the bottom rod by means of thedevice (40); lifting the device (40) via the cable (22) so as todisengage the mule shoe assembly and rotationally release the devicefrom the string; optionally, performing maneuvers to correct theinclination of the string; resuming the drilling and the supply ofdrilling fluid in the second duct (151) through the second fluidsupplying device (124); upon completion of the drilling, completelyremoving the device (40) from the rod string, pulling the device upwardby rewinding the cable (22), without unscrewing the rods of the string;bringing the valve member (30 a) into the closed position so as to closethe first central duct (15); lifting the string of rods while supplyinga consolidating fluid in the first central duct (15) through the firstfluid supplying device (123).